The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An airplane is moved by several turbojet engines each housed in a nacelle also housing a set of related actuating devices connected to its operation and performing various functions when the turbojet engine is running or stopped.
These related actuating systems in particular comprise a thrust reverser actuating system.
A nacelle generally has a tubular structure comprising an air intake upstream from the turbojet engine, a middle section intended to surround a fan of the turbojet engine, and a downstream section housing thrust reverser means and intended to surround the combustion chamber of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream from the turbojet engine.
This nacelle is generally intended to house a dual flow turbojet engine capable of using rotating fan blades to generate a flow of hot air (also called primary flow) coming from the combustion chamber of the turbojet engine, and a flow of cold air (secondary flow) that circulates outside the turbojet engine through an annular tunnel formed between the fairing of the turbojet engine and an inner wall of the nacelle.
The two flows of air are discharged from the turbojet engine through the rear of the nacelle.
During landing of an airplane, the role of a thrust reverser is to improve the braking capacity of said airplane by reorienting at least part of the thrust generated by the turbojet engine forward.
During this phase, the reverser obstructs the cold flow tunnel and orients said cold flow toward the front of the nacelle, thereby generating a counterthrust that is added to the braking of the wheels of the airplane.
The means used to carry out that reorientation of the cold flow vary depending on the type of reverser.
However, in all cases, the structure of a reverser comprises moving cowls that can be moved between a deployed position in which they open a passage in the nacelle that is intended for the deflected flow on the one hand, and a retracted position in which they close that passage on the other hand. These cowls may serve for deflection or simply to activate other deflecting means.
In the case of a grid reverser, also known as a cascade reverser, the flow of air is reoriented by cascade vanes, the cowl then serving only to slide so as to expose or cover said vanes, the translation of the moving cowl being done along a longitudinal axis substantially parallel to the axis of the nacelle.
Additional blocking doors, activated by the sliding of the cowl, generally allow the tunnel to be closed downstream from the vanes so as to optimize the reorientation of the cold flow.
Aside from its thrust reversal function, the sliding cowl belongs to the rear section and has a downstream side forming a jet nozzle with a variable section intended to channel the discharge of the flows of air.
This nozzle may supplement a primary nozzle channeling the hot flow, and is then called secondary nozzle.
To respond to the issues of adapting the section of the nozzle to the various flight phases, in particular the takeoff and landing phases of the airplane, a thrust reverser has in particular been proposed like that illustrated in FIG. 1.
This thrust reverser comprises cascade vanes 11 for at least part of the airflow of the turbojet engine on the one hand, and at least one cowl 10 translatable in a substantially longitudinal direction of the nacelle able to move alternatively between a closed position, in which it provides the aerodynamic continuity of the nacelle and covers the cascade vanes 11, and an open position, in which it opens a passage in the nacelle and exposes the cascade vanes 11, on the other hand.
The moving cowl 10 comprises an outer part 10a and an inner part 10b each mounted translatably; the outer part 10a (downstream side of the cowl 10) forms a jet nozzle intended to channel the discharge of the flows of air.
By dividing the moving cowl 10 into an inner part 10b and an outer part 10a that are at least partially movable independently from one another, it is possible to adapt the relative positions of the outer part 10a and the inner part 10b to the flight conditions so as to vary the section of the jet nozzle formed by the moving cowl 10 by varying the length of the inner aerodynamic line of the moving cowl 10, both when the moving cowl 10 is in the closed position and exposes the cascade vanes 11, and when the moving cowl 10 is in the open position.
One recurring problem lies in the actuating system proposed to provide maneuvering of the nozzle, during the different flight phases, both when the thrust reverser device is in the direct jet phase and when it is in the reverse jet phase. In fact, such a system must be able to command a variable jet nozzle section when the thrust reverser is locked in the closed position, the variable nozzle reciprocally being in a maximally deployed position when the thrust reverser is deployed.
Telescoping electric cylinders have already been proposed in which a first rod moves the inner part 10b of the cowl and a second rod, slidingly mounted in first rod, moves the outer part 10a of the cowl.
However, this solution is not optimal: such an electric cylinder generally presents actuating difficulties.
In fact, the second rod being movable relative to the base of the cylinder, it is difficult to group the actuating means together in said base of the cylinder, and the second rod must generally be equipped with its own motor, which will therefore also be movable.
To resolve these actuating difficulties, application FR 2,922,059 proposes a double-acting telescoping linear actuator comprising a base, intended to be attached to a stationary element of the reverser, and serving as a housing for a first rod whereof the rotation is blocked and which can be translated by means of a drive shaft intended to be connected to means for rotational driving, the first rod being intended to be attached by one end to the end part of the nozzle-forming cowl, the first rod supporting a second rod positioned in the extension thereof and intended to be attached by one end to the rest of the cowl to be moved, said second rod being able to be blocked in rotation and translated by means of a second drive shaft passing through the base and connected to rotational driving means.
In this actuator, the means for driving the rods comprise a motor capable of driving an input shaft by at least one differential, said differential on the one hand having a first output shaft connected to one of the first or second drive shafts, and on the other hand, a second output shaft connected to the second or first drive shaft.
A differential refers to any mechanical means making it possible to distribute a drive speed to several output shafts by distributing the kinematic force.
Such an actuator makes it possible, by driving the rods of the actuator by means of the differential, to move one or the other of the moving parts of the cowl through a single motor means.
Furthermore, such an arrangement makes it possible to group the actuating means of the two rods of the actuator together in the base of the latter.
However, the presence of the differential involves having two distinct drive chains, one for each of the drive shafts of the two parts of the cowl.
Consequently, the mass, bulk, and therefore cost of the actuating system are still affected.
This excess mass is additionally detrimental to the performance of the turbojet engine(s) and deteriorates them.
Furthermore, such a solution with multiple drive chains is complex to implement.